Metal containers subject to mechanical processes on said machines basically are those obtained in aluminum, alloys thereof, steel or other suitable materials with which containers for the beverage, food field or technical use are obtained; such metal containers, before being subject to the multiple operations in a sequence that modify the outer side surface thereof, can be subject to preliminary inner and/or outer coating and lithography of the outer side surface.
The metal containers processed on such types of machines preferably are subject to different types of processes by plastic deformation called “necking” or “tapering”, that is, processes that partially change the geometry of the container and the processes by plastic deformation called “shaping” which, on the other hand, globally change the geometry. The same metal containers can be subject to mechanical processes that consist in making recessed or projecting shaped impressions on predetermined portions of the side surface of the containers themselves; said last processes are generally referred to with the term “embossing/debossing”.
As known, in machines that operate at high speed and in continuous, in order to carry out the sequence of mechanical processes mentioned above, it is necessary to move the metal containers from one working tower to the next one.
In said machines, the multiple working stations present wheels or “stars”, suitable for receiving the metal containers for transferring and processing, whose outer crown is shaped with suitable pockets based on the diameter of the metal container to be processed; the transport of said metal containers from one working station to the next one takes place “at once”, that is, using the vacuum technique and suitable mechanical guides intended for conveying the metal containers themselves.
A drawback of the conventional transport devices lies in the fact that they are unsuitable for moving complex shaped containers, such as those of the “bottle can” and/or “contour can” type, increasingly requested on the market. In fact, such types of containers present complex shaping of the side surface that requires a high number of passages and a reduced cylindrical portion for gripping. The high number of passages and thus, of transfers “worsens” the traditional method of pick up with vacuum technique, since the use of guides for the direct conveying of the metal conveyors causes scratching that, if repeated, can cause damages to the side surface of the containers themselves.
Moreover, the reduced cylindrical portion and the shape of the container makes the vacuum pick up, already “critical” for simple containers (of the “pop-can”) difficult; the use of such technique implies a certain percentage of loss during the transfer from one working tower to the next one.
A further drawback is that the current transport devices present limits as regards the pick up strength that can be exerted on the containers and the movable mass.
A further drawback is that the traditional transport devices do not allow a high phase displacement between one working tower and the next one, without inducing faults and causing the reject of the container or the machine stoppage.
A further drawback is that such transport system is characterised by long tooling before operations on a container of different format can be carried out.